Vertical distribution of soil biota along elevation gradient in temperate and tropical climate.

Understanding the vertical distribution of soil biota is essential for predicting soil functioning, nutrient cycling, and ecosystem responses to environmental gradients such as elevation and climate. We studied the depth distribution of soil macrofauna, nematodes, and soil microbes (using phospholipid fatty acid analysis, PLFA), together with basic soil parameters, along an elevational gradient from approximately 90 to 2700 m a.s.l. in a temperate climate (Europe) and a tropical climate (Papua New Guinea). Soil profiles were sampled using hand-dug soil pits to a depth of 1 m.

The density of all faunal groups as well as microbial biomass decreased with increasing soil depth; however, the depth patterns varied among elevations. Soil biota reached the greatest depths at the lowest part of the gradient, particularly in alluvial soils characterized by a deep A horizon, and also at sites close to or above the tree line where A horizon was also quite deep. These results indicate that both soil development and elevation-related environmental constraints strongly influence the vertical distribution of soil organisms, highlighting the importance of considering soil mainly A horizon depth and landscape position when assessing biodiversity and ecosystem processes along elevational gradients.